In the current specifications of the third generation mobile networks (referred to as UMTS, Universal Mobile Telecommunication System), the system utilises the same well-known architecture that has been used by all main second generation systems. A block diagram of the system architecture of the current UMTS network is presented in FIG. 1. The UMTS network architecture includes the core network (CN), the UMTS terrestrial radio access network (UTRAN), and the user equipment (UE). The core network is further connected to the external networks, i.e. the Internet, PSTN (Public Switched Telephone Network) and/or ISDN (Integrated Digital Services Network).
The UTRAN architecture consists of several radio network subsystems (RNS). The RNS is further divided into the radio network controller (RNC) and several base stations (BTS, referred to as Node B in the 3 GPP specifications). In this architecture there are several different connections between the network elements. The Iu interface connects CN to UTRAN. The Iur interface enables the exchange of signalling information and user plane information between two RNCs. There is no equivalent interface to Iur in the architectures of the second generation mobile networks. The radio network layer (RNL) signalling protocol across the Iur interface is called the radio network subsystem application part (RNSAP). The RNSAP is terminated at both ends of the Iur interface by an RNC. The Iub interface connects an RNC and a Node B. The Iub interface allows the RNC to indicate the required radio resources to the Node, for example, to add and delete cells controlled by Node B to support communication of dedicated connection between UE and C-RNC(Control RNC), information used to control the broadcast and paging channels, and information to be transported on the broadcast and paging channels. One Node B can serve one or multiple cells. UE is connected to Node B through the Uu radio interface. UE further consists of a subscriber identity module (USIM) and mobile equipment (ME). They are connected by the Cu interface. Connections to external networks are made through Gateway MSC (Mobile Services Switching centre) (towards circuit switched networks) or GGSN [Gateway GPRS (Group Packet Radio System) Support Node] (towards packet switched networks).
The general protocol model for UTRAN Interfaces is depicted in FIG. 2, and described in detail in the following. The structure described is based on the principle that the layers and planes are logically independent of each other.
The Protocol Structure consists of two main layers, Radio Network Layer and Transport Network Layer (TNL). These are presented in the horizontal planes of FIG. 2. All UTRAN related issues are visible only in the Radio Network Layer, and the Transport Network Layer represents the standard transport technology that is selected to be used for UTRAN. UTRAN has certain specific requirements for TNL. For instance, the real time requirement, i.e. the transmission delay has to be controlled and kept small.
In the HS-DSCH (HS-DSCH, High Speed Downlink Shared Channel; HSDPA High Speed Downlink Packet Access) specification work the basic assumption is that the same transport solution that has been used for DSCH will be used for HS-DSCH also. In this application the term HS-DSCH is used to describe the channel or data stream between CRNC and Node B on Iub interface and therefore it should not mixed up with the HSDPA related transport channel, which is an internal channel between MAC-hs (Medium Access Control) and L1(Layer1) in Node B. In this solution dedicated transport bearer is reserved separately for each DSCH data stream between SRNC (Serving RNC) and Node B. FIG. 3 shows the radio interface protocol architecture with termination points. In logical model MAC-hs, which is inserted in Node B, locates below MAC-c/sh, which further is implemented in CRNC. The HS-DSCH FP (frame protocol) will handle the data transport from SRNC to CRNC (if the Iur interface is involved) and between CRNC and the Node B. The architecture supports both FDD (Frequency Division Duplex) and TDD (Time Division Duplex) modes of operation, though in the case of TDD, some details of the associated signalling for HS-DSCH are different.
The basic structure of HS-DSCH is assumed to be based on two architectures: an RNC-based architecture consistent with Release '99 architecture and a Node B-based architecture for scheduling. Moving the scheduling to the Node B enables a more efficient implementation of scheduling by allowing the scheduler to work with the most recent channel information. The scheduler can adapt the modulation to better match the current channel conditions and fading environment. Moreover, the scheduler can exploit the multi-user diversity by scheduling only those users in constructive fades. Furthermore, the HSDPA proposal has the additional potential to improve on the RNC-based HARQ architecture in both UE memory requirements and transmission delay. The scheduler for the HS-DSCH is therefore located in the Node B, wherein the HS-DSCH refers to the transport channel, which locates between MAC-hs and L1 internally in Node B.
There is no identification IE in Iub/Iur FP (FP, Frame Protocol) to identify a certain UE. Therefore the dedicated transport bearers were needed to identify a particular UE to enable the efficient usage of power control function over the radio interface. This means that number of required transport bearers to be reserved between SRNC and Node B is the same as the number of DSCH data streams. One UE can have several data streams. To make the system work properly, capacity i.e. bandwidth for each transport bearer has to be reserved according the reserved DSCH capacity over the radio interface. E.g. if the DSCH capacity in the radio interface is 512 kbps and there are 10 data streams sharing the channel the maximum required transport capacity is 10 times 512 kbps over Iub interface to ensure the QoS. And as the scheduling is done by MAC-sh in CRNC only one transport bearer is used in certain time frame. As a result a lot of bandwidth is wasted. This increases the need of the bandwidth resources.
The invention is characterised by what is disclosed in the independent claims.